Standard surgical procedures such as tissue resection for use in treatment of benign and malignant tumors of the liver and other organs have several key shortcomings affecting efficacy, morbidity and mortality. A fundamental issue in these shortcomings is the inability of the resection to be performed in a variety of cases. To help overcome this limitation a series of mono-polar radio frequency (RF) devices were designed for use in tissue ablation and resection. These mono-polar devices however have limited usefulness in typical clinical settings because they are overly complex and difficult to use, and result in time consuming procedures that can lead to auxiliary injury to patients through grounding pad burns. Further, these mono-polar tissue ablation devices are limited in the scope and size of the ablation that can be created, and exhibit poor consistency of ablative results along with an overall low efficiency. Typical known ablation devices are designed to pierce into that target tissue and ablate the tissue from the inside out. This method can result in uneven heating of the target tissue and result in tumor seeding due to repeated penetration and retraction from malignant tissue. Consequently, there is a need for a tissue ablation system that overcomes the shortcomings of these mono-polar tissue ablation devices.
Although certain multiple electrode RF ablation systems have been developed, such conventional systems generally suffer from significant drawbacks related to inadequate RF heating. RF heating results from electrical current flow through the ionic fluid that permeates biological tissue, typically between an electrode and ground pad. High temperatures, however result in decreased electrical conductivity resulting in an impedance spike or rolloff that precedes the end of active heating. Present multi-electrode RF ablation systems require current to be switched between electrodes so each electrode is active less than 100% of the procedure time. This can lead to rehydration of target tissue, and adds to the time required to complete a procedure. These systems are also vulnerable to the heat-sink effect of critical heat from the electrodes being drawn away by flowing blood, thus decreasing the temperature of ablation. These problems can result in high local recurrence rates in perivascular regions due to the inability to generate a sufficient amount of sustained heat necessary to fully ablate the target tissue.